1. Technical Field
The present invention relates to a fixing device, a fixing apparatus and an image forming apparatus.
2. Related Art
When an image is formed by use of an electrophotographic process, a fixing apparatus provided with at least one pair of fixing devices disposed in an image forming apparatus so as to face each other to form a contact portion is used, and a toner image formed on a recording medium such as a sheet is fixed.
As the fixing apparatus, one having a configuration where, with a so-called straight shaped fixing member such as a fixing roll in which the outer diameter thereof along the axial direction is constant or a fixing belt in which a thickness thereof across the widthwise direction is constant, a pressing force in the widthwise direction of a contact portion formed by a pair of fixing members that are disposed facing each other is controlled so as to press each other with a constant pressure, is generally widely use. However, fixing apparatuses having other configurations have been conventionally variously proposed.
For example, a fixing apparatus can be cited where a pressing force in the widthwise direction of a contact portion formed by a pair of fixing devices is controlled so as to be small toward the center portion and high on both end portions.
On the other hand, there is also proposed a process where a non-straight fixing device is used.
For example, a pressing rotating body where, in a pressing rotating body formed by forming a rubber layer on a metal core, the shape of the metal core of the pressing rotating body is formed with a diameter set at the maximum at a center portion and tapered down toward both ends, and a thickness of the rubber layer that covers the core metal is formed so as to get thinner on progression from the end portions toward the center portion, is proposed.
Furthermore, besides these, an elastic rotating body where, in an elastic rotating body having a rubber layer and a surface resin layer disposed on the rubber layer, the surface resin layer has a protrusion portion that is continuously disposed along a bus line direction and thicker than other in the layer thickness is proposed.